IC cards are expected to be used in various fields owing to their high security. IC cards have attracted considerable attention as new information recording mediums, particularly, as information recording mediums that will replace magnetic cards have come into wide use recently.
Generally, an IC card is fabricated by mounting an IC module of a COB (chip-on-board) configuration on a base card. Information is written to and read from the IC module by bringing the contacts of the IC module into electrical contact with the contacts of a R/W head (read/write head).
The IC module of the IC card has a substrate, and contacts to be connected to CLK (clock) lines, I/O lines, V.sub.cc lines (power lines), RST (reset) lines, GND (grounding) lines and such are formed on one surface of the substrate, semiconductor devices included in an IC chip mounted on the other surface of the substrate are connected electrically by wires to the contacts. The IC chip is sealed in an encapsulating resin.
Elements formed opposing surfaces of the substrate are electrically connected via through holes.
The base card of the IC card provided with the IC module is a flexible, thin polyvinyl chloride card body or the like. Therefore, physical failures are caused in the IC module sometimes by the bending of the base card and pressure being directly applied to the IC module.
One of the failures is the cracking of the IC chip. When the IC card is bent or the IC module is exposed directly to a pressure that induces a stress which the IC module is unable to withstand, cracks develop in boundaries between the contacts and the like. Some other physical failures are caused by the disconnection of the wires and the cracking of the resin.
For example, in a conventional IC module, a contact layer formed on a substrate is divided by isolation grooves formed therein across a region in which IC chips (semiconductor devices) are placed into contacts to be connected to a CLK line (clock line), an I/O line, a V.sub.cc line (power lines), a RST line (reset line), a GND line (grounding line) and such. Therefore, when the IC card is bent or a pressure is applied directly to the IC chip, a stress induced in the IC module is concentrated on portions of the substrate around the isolation grooves, and cracks often develop in those portions of the IC chip.
In most cases, cracks are liable to develop in boundary portions of the encapsulating resin on which bending stress is concentrated.